Apparatus for utilizing detonation waves



POWDER -mfd 1 20 70 a4 FUEL GAS PURGE GAS Sept. 29, 1964 OXIDANT- M A T TORNEV INVENTORS JOHN F. PEL ON LEWIS M.-CO DEN @QZMJMQ;

OXIDANT United States Patent 3,150,823 APPARATUS FOR UTILEZING DETONATION WAVES John F. Pelton and Lewis M. Cowden, both of Indianapolis, Ind., assignors to Union Carbide (Iorporatien, a corporation of New York Filed Oct. 4, 1961, Ser. No. 142,896 3 Claims. (Cl. 23Q79) The instant invention relates to an improved apparatus for utilizing detonation waves for coating and the like. More particularly it relates to an improved valve manifold for use in such an apparatus.

In U.S. Patent 2,714,563 of R. M. Poorman et al. which issued on August 2, 1955, apparatus is disclosed in which detonation waves are utilized to transmit energy to powder particles which are suspended in a detonated fluid charge. Utilizing this energy, the powder par-'cles are heated to a high temperature and accelerated to a high velocity, whereby they may be used to form coatings on surfaces of bodies.

In the method of operation of this apparatus, a charge of a detonatable fiuid mixture is first formed by feeding a fuel gas and oxidant through inlet valve means into a chamber where mixing takes place. The as-formed detonatable mixture is then passed to an elongated barrel and powder particles are suspended in the mixture as it enters the barrel. Upon admission of a proper charge, the fuel and oxidant valves close and through separate valve means a quantity of purging gas, such as nitrogen, is fed into the mixing chamber and across the fuel and oxidant valves. Thereupon, the detonatable mixture is ignited. The resulting detonation and associated ph nomena produce gaseous products which, due to the increased pressure within the apparatus, are forced out the open end of the barrel. This transmits energy to the suspended powder particles whereby they are heated, accelerated, and propelled out of the barrel.

The purge gas stream is intended to accomplish several purposes. First, it is supposed to blanket the fuel and oxidant inlet valves and prevent any bacloflash of the detonation from fouling the valves and impairing their operation. Second, it is supposed to sweep substantially all of the fuel gas and oxidant out of the mixing chamber and into the barrel before ignition of the detonatable mixture. This purge gas stream continues after the detonation is completed in order to sweep all the gaseous detonation products from the barrel.

The next operating cycle is then begun by closing the purging gas valve and reopening the fuel and oxidant .valves for the entry of fuel and oxidant to the mixing chamber for the formation of the next detonatable fluid mixture. Many of these cycles can be carried out per second.

It has been found that the apparatus of U5. Patent Number 2,714,563 (hereinafter referred to as standard equipment) presents certain difficulties which may adversely affect the coatings obtained. Occasionally the detonation gun performs in an erratic manner producing certain undesirable results. Investigations of the gun operation have shown that the detonation mixture may vary in composition along the length of the gun barrel. A detonatable mixture theoretically containing 49.5 vol. percent oxygen has been found to vary from 42 to 56 volume percent in oxygen content along the barrel. It is known that the ratio of fuel to oxidizing gas affects the velocity of the detonation wave. Also, the oxidizing or reducing atmosphere has a corresponding chemical affect on the coating powder. It is the variation in oxidant-fuel ratio, although small, which is believed to be responsible for the erratic coating behavior of the detonation gun at times. The timing of the opening and closing of the oxidant and fuel gas valves has been varied in an attempt to maintain a constant composition, but this has, for the most part, been unsuccessful.

Accordingly, it is the main object of the present invention to provide improved apparatus for the utilization of detonation waves, wherein the fluid fuel and oxidant are introduced in such manner as to maintain a reasonably constant detonatable mixture composition along the length of the detonation gun barrel.

It is a further object to provide such improved operation by constructing the inlet valve manifold in such a way as to obtain uniform mixing of the oxidant and fuel gas.

It is still a further'object to provide such improved operation by obtaining uniform oxidant and fuel gas mixing and also uniform purging of both the oxidant and fuel gas valves prior to detonation initiation.

Other objects and advantages will be apparent from the description and drawings in which:

FIGURE 1 shows a schematic view in section of an improved apparatus utilizing detonation waves constructed with a preferred form of valve manifold so that a uniform detonataole mixture is introduced to the detonation gun barrel.

FIGURE 2 is a similar vi w of another embodiment of such an apparatus.

FIGURE 3 is in a view of still another embodiment of such an apparatus.

Fl URE 4- is a sectional schematic view of viscous dampening flow control means used in the gas inlet conduits.

The objects of the invention are accomplished in general by providing in a detonation gun having an elongated barrel, such barrel having an open end and of such length and diameter to permit the formation and propagation in a fluid fuel charge of a detonation, a valve manifold communicating with said barrel having therein a mixing chamber, fuel and oxidant gas inlet valves communicat ing with such mixing chamber, and conduit means including a pur ing gas valve for controlling the supply of a purging gas positioned and arranged to pass the purging gas over said fuel and oxidant inlet valve when said valves are closed, the improvement which comprises providing in said valve manifold paths which are substantially identical in length and resistance to flow for both the oxidant and fuel gas between the inlet valves and the point where they leave the mixing chamber.

Further advantages are obtained by additionally providing separate paths within the manifold for the purging gas valve to the oxidant valve and the fuel gas valve.

till further advantages are obtained by providing in a gas mixing chamber fuel and oxidant inlet valves such that the gas flow paths from each inlet valve to the outlet of the gas mixing chamber are equal in length and resistance to flow and also providing a purging gas inlet to such gas mixing chamber such that the purging gas can flow in substantially equal amount over said oxidant and fuel valves when they are closed to completely sweep all the oxidant and fuel gases from the mixing chamber prior to ignition of the detonata'ole gas mixture.

Still further advantages are obtained by employing viscous dampening flow control means in each of the oxidant and fuel gas inlet conduits.

Referring specifically to the embodiment of FIGURE 1, a detonation gun is provided with an elongated barrel ill, powder entry tube means 12 for supplying powder to said barrel, ignition means 14, including a spark plug 16, and valve manifold 18 at one end of barrel 1%, the barrel being open at the other end thereof.

Valve manifold 18 contains a mixing chamber 2 wherein a fuel gas and an oxidizing gas are mixed to 3 form a detonatable gas mixture before passage to the barrel it) of the gun.

Fuel gas, such as acetylene, passes from a suitable source (not shown) through fuel conduit means 26) and fuel gas valve means 22 to chamber '70 of valve manifold 18. Concurrently therewith, oxidant, such as oxygen, passes from a source (not shown) through oxidant conduit means 26 and oxidant valve means 2% to chamber 72 of valve manifold 13. Fuel gas chamber 7t? and oxidant chamber 72 are connected together at mixing chamber 24 through lines 76 and 73 which are substantially identical in size and length.

A stream of purging gas, such as nitrogen, passes from a source .(not shown) through purging gas conduit means 39 and purging gas valve means 32 to purging gas chamber 34 of valve manifold 18. Chamber 34 is connected to oxidant chamber '72 and fuel gas chamber 7%) through purge lines dd, 82, and '34. This improved apparatus not only provides equal feed of oxidant and fuel to the detonation gun barrel but also provides eflicient and complete purging of the oxidant and fuel-gas valve'areas prior to detonation initiation.

As described at great length in US. Patent Number 2,714,563, the operating cycle for the detonation gun is .as follows:

An electric motor 40 is belted to shaft 42 with three cams 4'4, 46, and 4.3. Cam 44 regulates the opening and closing of fuel and oxidant valves 22 and 28. Upon the opening of these valves, charges of these gases pass to mixing chamber 24 and then into barrel 1th of the gun. A quantity of powder is suspended in the detonatable mixture as it passes powder entry means 12 in the barrel 10. When a sufficient charge of detonatable mixture has been admitted to the barrel lil, cam 44 closes valves 22 and 28, while cam 46 rotates to the position at which the purging gas valve 32 opens. The purging gas stream then flows across the closed valves 22 and 28 and up to the spark plug 16 sweeping all the oxidant and fuel gas out of the valve manifold. At this point in time, cam 48 closes the ignition circuit through switch 50, thereby energizing the circuit containing battery 52 and spark coil 54. The spark coil delivers a spark voltage to spark plug 16, and the detonatable mixture in the barrel is ignited. A detonation and associated phenomena then occur to develop the energy which propels the suspended powder and combustion products at high velocity and temperature from the open front end of barrel It).

It has been found that the provision of substantially identical paths both in distance and flow resistance for oxidant and fuel from inlet valve to outlet of mixing chamber has desirable results in that the detonatable mixture is substantially constant in gas compostion within 1 /2 vol. percent along the barrel length. This has enabled consistently satisfactory and uniform coating results to be obtained.

FIGURES 2 and 3 show alternative forms of the valve manifold 18 of FIGURE 1. Like numerals are used in those figures to identify like parts.

In the embodiment of FIGURE 2, fuel gas valve 22 and oxidant valve 28 are positioned in the side of mixing chamber 24 transverse to the longitudial axis of the chamber (measured from inlet to outlet) in such fashion. that the distances from both valves to the outlet conduit 86 of chamber 24 are substantially identical. Purge gas from .purge valve (not shown) enters the chamber through inlet conduit 88 and can very effectively sweep over the valves and out through the outlet. This removes all the fuel and oxidant from the chamber and tends to maintain substantially constant gas composition along the barrel. Bafiile means 90 may also be used at the purge gas inlet position of chamber 24 in order to spread at the purge gas stream evenly across the chamber and the valves.

In the embodiment in FIGURE 3, the fuel gas valve 22 and oxidant valve 28 are positioned transversely to the longitudinal axis of mixing chamber 24 and are in op- ,is eae posing relatioin. Purge gas enters through conduit 88 and leaves through conduit $6.

With any of the three above disclosed embodiments of the invention the detonation gun may be operated in a manner which substantially improves both the quality of coatings obtained and also the uniformity or consistency of successive coatings.

A further improvement of the present invention which is preferably used with the embodiments of FIGURES 1-3 is shown in FIGURE 4. In this embodiment viscous dampening flow control means is used in both "the fuel gas inlet conduit 2%, and the oxidant inlet conduit 26. This flow control means is positioned as close to the inlet valve as possible. The control means 92 consists of a chamber 94 filled with gas flow restricting means such as a plurality of balls /d. Alternatively the gas flow restricting means within the chamber 94 could consist of V a plurality of small diameter tubes aligned along the longitudinal axis of the chamber. The important characteristic of this flow control device is a means for dampening flow variations with minimum pressure drop.

The purpose of the viscous dampening flow control means is to provide substantially equal flow characteristics for the oxidant and fuel gas streams. While the proper gas passages and supply pressures are used to provide the desiredflow rates, the different gas viscosities may provide undesirable gas mixtures. For example, when the inlet valve is opened, the built-up pressure in the supply conduit forces the gas but the valve opening.

low viscosity gas begins to flow rapidly and then the flow begins to decrease as the gas pressure in the conduit decreases. A high viscosity gas, on the other hand, initially has a low flow rate which gradually increases. When a mixture of acetylene and oxygen is used, the initial mixture, will be rich in the lower viscosity acetylene while the mixture formed near the end of the gas inlet cycle will be rich in the higher viscosity oxygen. The

. viscous dampening means will reduce the initial surges 7 of balls 96 will depend upon the particular gas flow desired and the flow characteristics of the upstream gas supply system. In one installation employing an oxygen/ carbon ratio of 0.98 the viscous dampening means in the oxygen line was about 2 in. OD. and 10 in. long and contained 200 /s in. diameter steel balls. The viscous dampening means'in the acetylene line was about 2 in. OD. and 10 in. long and contained 275 /s-in. diameter steel balls. The chambers each had a 0.280 inch diameter outlet orifice for use in calibration of the gas flow. These numerical values are not limitations to the present invention and are merely illustrative.

As stated previously, operating a detonation gun in accordance with the instant invention has been found to improve the consistency of the oxidant-fuel gas composition along the barrel from about ;':7 volume percent to 10.5 volume percent. This decrease in composition variation has greatly improved the overall results of coating processes due to the critical-ity of the oxidant-fuel gas ratio in the detonation reaction. As a result the number of rejects on coated parts in production has been substantially reduced.

Analysis of the micro-structure of coatings applied utilizing the instant invention shows that there is essentially no difference in the coatings made with the new valve system and the old system with respect to crystalline phases present and general structure. However, the coatings made with the new system exhibit a more uniform distribution of constituents and a reduction in the number of turbulent areas which generally are responsible for large pits.

Examination of various ground surfaces has shown a dcfi i fi reduction in the number of large pits. An indication of this improvement was shown in an experiment on pump bushings in which six bushings were coated with standard equipment and six bushings were coated using the new valve system. After grinding and lapping, it was found that every bushing coated with standard equipment had at least one large pit. In contrast to this, in all sixbushings coated with the new valve system only one such it was found.

Thus it may be seen that the instant invention not only improves the regulation of oxidant to fuel gas ratios but also results in more homogeneous coatings and elimination of pits to a large extent.

This application is in part a continuation of our copending application Serial No. 825,237 filed July 6, 1959, now abandoned.

What is claimed is:

1. In a detonation gun having an elongated barrel provided with an open end, of length and diameter to permit the formation and propagation in a fluid fuel charge of a detonation, a valve manifold communicating with said barrel having therein fuel, oxidant and purging gas inlet valves, a mixing chamber and conduit means for controlling the supply of a purging gas positioned and arranged to pass a purging gas over said fuel and oxidant inlet valves when said valves are closed, the improvement which comprises separate chambers within said valve manifold adjacent the oxidant, fuel gas and purge gas valves, a mixing chamber within said valve manifold opening into the gun barrel and connected to the chambers adjacent the oxidant and fuel gas valves by two conduits of substantially the same length and cross-section, and conduit means between the chamber adjacent the purging gas valve and each of the chambers adjacent the oxidant and fuel gas valves for supplying separate streams of purging gas thereto.

2. In a detonation gun having an elongated barrel provided with an open end, of length and diameter to permit the formation and propagation in a fluid fuel charge of a detonation, a valve manifold communicating with said barrel having therein a mixing chamber, fuel and oxidant gas inlet valves communicating with such mixing chamber, and conduit means including a purging gas valve for controlling the supply of a purging gas positioned and arranged to pass a purging gas over said fuel and oxidant inlet valves when said valves are closed, the improvement which comprises providing in said valve manifold paths which are substantially identical in length and resistance to flow for both the oxidant and fuel gas between the inlet valves and the point where they leave the mixing chamber and wherein the mixing chamber has a longitudinal axis from the chamber inlet to the chamher outlet, the oxidant and fuel gas inlet valves are located adjacent each other in one wall of the chamber transverse to the longitudinal axis of the chamber such that the distances from both valves to the chamber outlet are essentially identical and wherein means are provided for introducing purge gas through the chamber inlet.

3. An apparatus as set forth in claim 2 wherein a baffle is positioned at the chamber inlet to spread out the purge gas stream evenly across the chamber and the valves.

References Cited in the file of this patent UNITED STATES PATENTS 

2. IN A DETONATION GUN HAVING AN ELONGATED BARREL PROVIDED WITH AN OPEN END, OF LENGTH AND DIAMETER TO PERMIT THE FORMATION AND PROPAGATION IN A FLUID FUEL CHARGE OF A DETONATION, A VALVE MANIFOLD COMMUNICATING WITH SAID BARREL HAVING THEREIN A MIXING CHAMBER, FUEL AND OXIDANT GAS INLET VALVES COMMUNICATING WITH SUCH MIXING CHAMBER, AND CONDUIT MEANS INCLUDING A PURGING GAS VALVE FOR CONTROLLING THE SUPPLY OF A PURGING GAS POSITIONED AND ARRANGED TO PASS A PURGING GAS OVER SAID FUEL AND OXIDANT INLET VALVES WHEN SAID VALVES ARE CLOSED, THE IMPROVEMENT WHICH COMPRISES PROVIDING IN SAID VALVE MANIFOLD PATHS WHICH ARE SUBSTANTIALLY IDENTICAL IN LENGTH AND RESISTANCE TO FLOW FOR BOTH THE OXIDANT AND FUEL GAS BETWEEN THE INLET VALVES AND THE POINT WHERE THEY LEAVE THE MIXING CHAMBER AND WHEREIN THE MIXING CHAMBER HAS A LONGITUDINAL AXIS FROM THE CHAMBER INLET TO THE CHAMBER OUTLET, THE OXIDANT AND FUEL GAS INLET VALVES ARE LOCATED ADJACENT EACH OTHER IN ONE WALL OF THE CHAMBER TRANSVERSE TO THE LONGITUDINAL AXIS OF THE CHAMBER SUCH THAT THE DISTANCES FROM BOTH VALVES TO THE CHAMBER OUTLET ARE ESSENTIALLY IDENTICAL AND WHEREIN MEANS ARE PROVIDED FOR INTRODUCING PURGE GAS THROUGH THE CHAMBER INLET. 